In recent years, attention has been directed to a metal nitride as a material such as a raw material of an aluminum nitride used for a semiconductor device, a metal sliding member, an electrode construction material and the like. Many fluorescent materials using a metal nitride have also been found, and the demand as the raw material has also increased. A high-purity product is required for the metal nitride used for the applications.
Examples of a conventional method for producing a metal nitride include a method for heating alkaline earth metals such as calcium in a nitrogen gas stream (Non Patent Literatures 1 and 2).
However, this method nitrides only the surfaces of a metal, and has difficulty in nitriding the inside thereof. Therefore, the metal nitride obtained by the method cannot be used for the above-mentioned application like a semiconductor device requiring a high-purity product.
Another method is a method for heating calcium with ammonia, a problem of which method is production of a calcium hydride as a by-product (Non Patent Literature 3). Furthermore, yet another method is a method for heating tricalcium tetranitride to 250° C., problems of which are explosiveness and toxicity (Non Patent Literature 4).
Furthermore, there is disclosed a method for reacting a molten zinc-calcium alloy with a heated and pressurized nitrogen jet to synthesize a calcium nitride (Patent Literature 1). However, this method requires a special device, and thus it is difficult to say that the method is an industrially advantageous method.